Research On Wastewater Pollutant's Degradation And DPBs Sludge's Characteristic In A₂N System

In wastewater biological nitrogen and phosphate removal processes, microorganisms need to consume certain organic carbon sources both in denitrification and phosphorus uptake. But municipal sewage's low and insufficient carbon source often makes it hard to satisfy the request of high efficient phosphorus and nitrogen removal in the meantime. Therefore, it is necessity to look for high efficient nitrogen and phosphate removal technique. The mechanism of"one carbon, two use"to carbon source of the denitrifying phosphate-accumulating organisms (DPBs for short) provides new solution for the carbon source shortage problem in the wastewater treatment.Based on the theory of denitrifying dephosphatation, the continuous-flow Anaerobic-Anoxic/Nitrification process (A2N) was used in this investigation. First, the removal effects of COD, nitrogen and phosphorus, DPBs'characteristic of absorbing carbon and DPBs sludge's characteristic were studied. Then translation of system internal cell depositor matter were researched. Finally the removal characteristic of A2N continuous influent system and its main impact factors were studied.The conclusions of monitoring for a year are following:(1) The continuous-flow A2N process has stable removal effects to organic matter, nitrogen and phosphorus. The average removal rates of COD, TN, NH4+-N, TP are 86.7%, 70.50%, 83.54%, 69.72% separately. Comparing to conventional A2O process, A2N process has the superiority of low carbon requirements of sewage and low aeration.(2) In the continuous-flow A2N system, DPBs absorb more organic matter from wastewater in the anaerobic phase , the PHB generated more, and then the PHB consumed more which is following the sludge returned to the anoxic phase. On the whole, the continuous-flow A2N system has a higher removal rate of nitrogen and phosphorus. (3) In the continuous-flow A2N system, at the same reaction time, as the sludge concentration increases ,system's phosphate release rate, phosphate uptake rate and denitrification rate are increasing along, but the unit sludge phosphate release rate, phosphate uptake rate and denitrification rate are falling along. At the same sludge concentration, as the reaction time increases, system's phosphate release rate and uptake rate are subsequently reducing.(4) The results showed that, in the continuous-flow A2N system, the approximate phosphorus content of DPBs sludge fluctuates between 3.2%~4.1%. The proportion of denitrifying phosphate-accumulating organisms to total phosphate-accumulating organisms is 66.23%.(5) The results of continuous operation of the system showed that, the continuous-flow A2N system is appropriate to be used to treat low carbon source wastewater. It can also obtain a stable and efficient removal rates of nitrogen and phosphorus when the C/N is 3.16~6.10.